1. Field of the Invention
The present invention relates to a method and a machine for reducing the thickness of a stone slab to a desired dimension.
2. Description of the Prior Art
Slabs of stone, such as marble and granite, are machined and polished for use as table tops, pedestals, sculpture bases and for other decorative and structural purposes. To render a stone slab suitable for such an application it is often necessary to work a stone slab by reducing its thickness so as to create a smooth, uniform expansive surface, and then polishing that surface. The surface thus exhibits a clean, attractive sheen.
Some slabs used for decorative and structural articles of the type described have heretofore been reduced in thickness by grinding so as to achieve a uniform slab thickness and a smooth surface area. In such a procedure grinding wheels or grinding rollers having grinding surfaces formed of an abrasive, such as carborundum, are mounted for rotation above a horizontal bed across which the stone slab to be finished is passed. In one such prior art system a plurality of grinding wheels are mounted above the supporting bed for rotation about separate vertical axes. The circular grinding surfaces of the wheels are faced with carborundum or some other abrasive material. These grinding surfaces bear downwardly upon the slab to be finished. The several grinding wheels employed are arranged in a staggered pattern so that each grinding wheel will grind a swath of material from the stone slab as the slab passes in a linear path therebeneath Collectively the grinding wheels thereby cover the entire surface of the slab.
Conventional grinding machines and grinding processes of the type described are extremely time consuming. The time required to grind material from the face of a stone slab increases with the depth of material to be ground away. These prior grinding systems are also limited in the depth of stone which can be ground away. For example, such conventional systems are limited to grinding away about one-quarter of an inch of thickness of a four foot by eight foot granite slab, which is a typical size in the industry. Reduction of the thickness of such a slab by one-quarter of an inch, using a conventional system and according to a conventional method, requires approximately four or five hours. During this time the machine must be constantly attended. Thus, the number of stone slabs which can be reduced in thickness during a normal work shift is quite limited, thereby contributing substantially to the cost of finishing stone slabs in this manner.